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- Structural characterization of exopolysaccharides obtained from Porphyridium cruentum exhausted culture mediumPublication . Cristofoli, Nathana L.; Ribeiro Lima, Alexandre; Rosa Da Costa, Ana; Evtyugin, Dmitry; Silva, Carlos; Varela, João; Vieira, MargaridaMicroalgae produce and secrete large quantities of polysaccharides into the culture medium that is discarded when biomass is separated. The main objective of this study was to add value to the exhausted culture medium (ECM) of Porphyridium cruentum through the recovery of extracellular polysaccharides (EPS) by different extracting and purifying methods for the future biotechnological applications. The ECM was submitted to pre-cipitation with cold absolute ethanol, using ultrasound, dialysis, and trichloroacetic acid (TCA) as purification methods. The purification provided a lower yield, with higher car-bohydrate content. The TCA purified sample presented up to twice as much total carbo-hydrates as the non-purified samples, mainly composed of xylose, galactose, and glucose. Scanning Electron Microscopy (SEM) images showed the smooth structure of P. cruentum EPS, in which TCA post-treatment and dialysis allowed obtaining larger and purest par-ticles, being a good candidate for film making. Microalgal polymeric by-products are a sustainable source to recover valuable compounds, and the purification treatment proved to be an important step to valorize this material.(c) 2023 The Authors. Published by Elsevier Ltd on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY-NC-ND license (http://creati-vecommons.org/licenses/by-nc-nd/4.0/).
- Comparative study of the production of cellulose nanofibers from agro-industrial waste streams of Salicornia ramosissima by acid and enzymatic treatmentPublication . Ribeiro Lima, Alexandre; Cristofoli, Nathana L.; Rosa Da Costa, Ana; Saraiva, Jorge A.; Vieira, MargaridaThe study of the suitability of two isolation processes to produce cellulose nanofibers (CNFs) from Salicornia ramosissima waste, with potential applicability as a reinforcing agent of polymeric composites was carried out. To separate the cellulose fibrils from the cell wall and obtain CNFs an alkaline treatment was applied followed by a bleaching treat-ment and, the insoluble residue was next hydrolyzed by either an acid treatment (AT) or an enzyme treatment (ET). SEM and TEM images indicated fiber exposure caused by both treatments. The diameter, length, aspect ratio, and polydispersity index, were measured for both CNFs. CNF (ET) showed high zeta potential values suggesting that ET produces more electrically stable and thinner nanofibers. The FTIR spectra revealed that both treatments effectively removed the amorphous components allowing the CNFs isolation, and XRD patterns evidenced the increase in the degree of crystallinity of both CNFs. Nonetheless, CNF(AT) presented a lower mechanical resistance due to its smaller particle size, compared to the CNF(ET). In summary, the (ET) could successfully isolate CNFs from the Salicornia waste, encouraging the use of this treatment, once when compared to (AT), it does not generate toxic residues, presents mild thermal conditions, and produces CNFs with higher-value applications.